Solar energy is a strong candidate. It could prove to be a relatively cheap source of power for a lunar base, especially since many of the raw materials needed for solar panel production can be extracted on site. However, the long lunar night (14 Earth days) is a drawback for solar power on the Moon. This might be solved by building several power plants, so that at least one of them is always in daylight. Another possibility would be to build such a power plant where there is constant or near-constant sunlight, such as at the Malapert mountain near the lunar south pole, or on the rim of Peary crater near the north pole. See Peak of Eternal Light.
The solar energy converters need not be silicon solar panels. It may be more feasible to use the larger temperature difference between sun and shade to run heat engine generators. Concentrated sunlight could also be relayed via mirrors and used in Stirling engines or solar trough generators or it could be used directly for lighting, agriculture and process heat. The focused heat can also be employed in materials processing to extract various elements from lunar surface materials.
source URL: http://en.wikipedia.org/wiki/Lunar_base